There is an ever increasing need for new, more effective, efficient and lower cost methods for decontaminating water and other water based (aqueous) liquids. As an example, Center for Disease Control and Prevention (CDC) reports in a Mar. 6, 2003, report on BACTERIAL WATERBORNE DISEASES that each year there are 3.5 billion episodes of illness and a resulting three million estimated deaths caused by contaminated water and despite global efforts improvements have barely kept pace with population increases. From an Emerging Infectious Diseases article, dated 10 Oct. 2005, it was reported that seventeen percent of all deaths of children under five years of age in the developing world was caused by contaminated water. With these statistics, it is astounding that no water purification method is currently available and sufficiently low in cost to prevent such water borne illnesses. The simplicity and associated potential low cost of manufacture and operation of devices made according to the instant invention promise to make substantial in-roads toward a solution to these problems.
A profound example of changes in methods of water purification is a new water treatment plant located in Salt Lake City, Utah. Rather than chlorine, this plant employs ozone and ultraviolet light, as ultraviolet light is more effective than chlorine in terms of decontaminating water containing cryptosporidium and other chlorine resistant microbes. However, use of light is known to sometimes be ineffective and at other times be unpredictable when used in water that has variable light transmission quality.
While decontamination and purification are terms generally considered in an ultimate context of complete elimination of any and all undesirable contaminants, it is generally known, as disclosed on page 68 of Principles and Methods of Sterilization, 2nd Edition, published by Charles C. Thomas, Springfield, Ill., in 1983, that one hundred percent sterilization should never be considered as completely attained. Rather, biological contaminants should be considered to be eliminated logarithmically, such as being measured by time constants dependent upon intensity and method of treatment.
To codify a standard for sterilization, the Association for the Advancement of Medical Instrumentation (AAMI), 110 N. Glebe Road, Suite 220, Arlington, Va. 22201-4795 has issued a proposed standard for selecting appropriate Sterility Assurance Levels (SALs) (See Proposed Standard on Selecting Appropriate Sterility Assurance Levels published as an Internet bulletin on Feb. 10, 2000). While, SALs are generally used to determine levels of sterilization for medical products, a similar standard may be considered for water and other aqueous liquid purification, as well. AAMI reports, as examples, that items which come into contact with skin may need only an SAL of 10−3 while implants or IV injectable liquid pathway products should be sterilized to an SAL of 10−6.
Similar considerations might be applied to water purification. Drinking water from one source might be sufficiently pure at an SAL of 10−3 while another source might require an SAL of 10−4 or better. It may also be desired to have a single water purification or sterilization system which could be used for various purposes (e.g. for drinking water or for a medical application). Also, such aqueous liquids as milk might require different sterilization for different packaging and storage requirements. This invention is meant to fulfill a variety of applications related to meeting requirements for a variety of sterilization levels.
A number of U.S. Patents cite methods and apparatus for achieving various levels of sterilization of aqueous liquids. An example of such a patent is provided by U.S. Pat. No. 6,136,362, issued Oct. 24, 2000, to Roger J. Ashton (Ashton), titled HIGH TEMPERTURE/SHORT TIME PASTEURIZATION SYSTEM AND METHOD OF CLEANING. Ashton particularly teaches a way of cleaning a system used for pasteurization of milk. While pasteurization has long been used to improve safety and lengthen term for storage of milk, pasteurized milk has also been recognized as still containing microbes and, therefore, is not completely sterilized. Even so, continuous flow pasteurization is not taught in Ashton, but rather Ashton teaches a system for cleaning a pasteurization circuit without connecting and disconnecting apparatus. Also, Ashton does not teach regulating pressure at a temperature required for sterilization.
Another U.S. Pat. No. 5,403,564 issued Apr. 4, 1995 to Helmut Ketschnig et al. (Ketschnig), titled APPARATUS FOR HEATING AND THERMAL DECONTAMINATING A PUMPABLE OR POURABLE MATERIAL, discloses apparatus for heating and thermal decontamination using a microwave unit. As such, Ketschnig makes no attempt to insure that non-sterile material will not contaminate a conduit leading from the microwave unit to a discharge tube. In other words, Ketschnig sterilizes by means of radiation and assures any achieved sterilization only within the zone of radiation.
A U.S. Pat. No. 6,673,311 B1 issued Jan. 6, 2004, to Kazuyoshi Sotoyama, et al., (Sotoyama) titled METHOD AND APPARATUS FOR CONTINUOUS HEAT STERILIZATION OF LIQUID, discloses sterilization by heating and rapid release of pressure. As such, Sotoyama employs a rapid high pressure release (which may be a pressure drop in the range of 2 to 100 MPa). Such an initial pressure is much higher than pressure employed in the instant invention which is in the range of 0.2 to 0.5 MPa, and no rapid pressure release is employed in the instant invention.
U.S. Pat. No. 6,579,494 B1 issued Jun. 17, 2003, to Jacques Chevallet, et al. (Chavallet) and titled PROCESS AND DEVICE FOR STERILIZING AND DISPENSING A LIQUID FOR MEDICAL USE discloses method and apparatus for sterilizing liquids for medical use. As such, Chavellet discloses and claims a validating structure which permits and requires a “means for validating a sterilization treatment” resulting from an implemented adjustable heating apparatus. Chevallet makes an interesting point relative to checking a 10−6 level of viable microorganisms in a continuous flow apparatus, saying that such a check according to Poisson probability is unachievable.
U.S. Pat. No. 9,211,351 issued December 2015 to John G. Bowen (BOWEN) and titled METHODS FOR VARIABLY STERILIZING AQUEOUS LIQUIDS discloses a continuous flow sterilizer. BOWEN teaches employing apparatus operating at substantially fixed temperatures and pressures at variable flow rates to achieve a predetermined SAL.
Commonly, recently allowed patents disclose continuous flow systems which rely upon temperature, pressure and a given dwell time to accomplish a desired SAL. As an example, see U.S. Pat. No. 9,757,485, titled SYSTEM AND METHOD FOR FLUID STERILIZATION and awarded to Papadopoulos, et al., Sep. 12, 2017. However, recent studies have shown that in a volume of water raised to a predetermined kill-temperature, achievement of an associated SAL in substantially instantaneous, not requiring monitoring of pressure or requiring a prescribed dwell time. The instant invention disclosed herein is therefore based upon measurement of a single parameter, temperature.